As semiconductor devices have become more highly integrated in recent years, circuit interconnections have become finer and distances between those circuit interconnections have become smaller. In the case of photolithography, which can form interconnections that are at most 0.5 μm wide, it is required that surfaces on which pattern images are to be focused by a stepper should be as flat as possible because the depth of focus of an optical system is relatively small. In order to planarize such a semiconductor wafer, there has been used a polishing apparatus for performing chemical mechanical polishing (CMP).
This type of polishing apparatus comprises a polishing table having a polishing pad (polishing cloth) attached thereon, and a top ring for holding a workpiece to be polished, such as a semiconductor wafer, in a manner such that a surface to be polished faces the polishing table. The polishing pad has an upper surface serving as a polishing surface. In this polishing apparatus, the polishing table and the top ring are independently rotated, and, while an abrasive liquid (slurry) is being supplied onto the polishing pad, a workpiece is pressed against the polishing pad on the polishing table at a predetermined pressure by the top ring. Thus, a surface of the workpiece is polished to a flat mirror finish.
When such a polishing apparatus is used to polish a workpiece, in order to achieve a desired polishing performance, it is required to adjust vertical positions of components in the top ring at the time of polishing. Conventionally, block gauges have been used to adjust vertical positions of the components in the top ring. Specifically, block gauges having a predetermined thickness are interposed between the polishing surface and the components, and then the top ring is lowered until the top ring is brought into contact with the block gauges on the polishing surface. Thus, vertical positions of the components at the time of polishing are adjusted by the block gauges.
However, according to the conventional method, it is necessary to manually adjust the vertical positions of the components with the block gauges. Therefore, it troublesome and time-consuming to adjust the vertical positions of components in a top ring according to the conventional method. Further, with regard to components which have not been adjusted in vertical position with block gauges, once such components are worn, the vertical positions of the components cannot be readjusted according to the conventional method.